1. Field of the Invention
The present invention relates to a method and an apparatus for preventing surface contamination and degradation of a device surface of a substrate while it is being transferred from one processing unit to another processing unit in a semiconductor device manufacturing line.
2. Description of the Related Art
Circuit integration density for semiconductor devices has been remarkably increasing in recent years, and thickness of a layer deposited on or etched from the substrate in a single unit process has become much smaller. In manufacturing such multilayered devices, it is necessary to repeatedly apply deposition and etching treatments in individual processing operations. As the number of such operations increases, there is a corresponding increase in the potential for contaminating the processed surface by particles and molecules, resulting from exposure to unfavorable environments or degradation due to chemical interaction.
For example, when a pure silicon surface is exposed to an air atmosphere even for a few seconds at room temperature, the surface becomes coated with a natural oxide (of thickness of about 50 xc3x85) which causes surface degradation or changes in the surface character, and furthermore, adsorption (molecular contamination) of various gaseous species in the air such as N2, O2, CO2, etc. can occur on the outermost surface, as well as adhesion of particulates such as organic matters, oxides, metals, ions, etc. floating in the air to cause particulate contamination on the device surface. Such degradation and changes in the substrate surface characteristics and molecular/particulate contamination on the device surface will adversely affect the subsequent processes, and are considered to be the primary cause of performance problems in the finished devices.
It is an object of the present invention to provide a method and apparatus for providing surface protection of substrates such as semiconductor wafers while they are being transported from one unit process to another unit process, by preventing their exposure to unfavorable environments that may cause surface contamination and degradation.
The object has been achieved in a method for protecting a substrate comprising: coating at least a part of a surface of the substrate with a coagulated film. The method may be conducted in a semiconductor device manufacturing line that repeatedly performs a plurality of stepwise processes of forming film layers, etching and removing portions of film layers wherein as-processed surface conditions are exposed to an atmosphere that may contaminate and degrade the device surface.
Another aspect of the invention comprises: coating at least a part of a surface of the substrate with a coagulated film, and transporting the coated substrate to a processing apparatus for conducting a subsequent step.
The subsequent step may be a wet-process step or a dry-process step, or a storage process, etc. The coagulated film may be comprised by an ice film, and the ice film may be produced with a deionized or ultrapure water. The substrate may be a semiconductor wafer or a liquid crystal substrate. The substrate may be preferably coated without exposing the surface to an environmental atmosphere. The substrate may be coated by coagulating liquid film formed on the surface which is formed in a dike formed on the surface. The substrate may be coated by coagulating vapor surrounding the surface.
Another aspect of the invention is an apparatus for processing a substrate comprising: a coating apparatus for coating at least a part of a surface of the substrate with a coagulated film, a processing apparatus for conducting a processing step on the substrate, and a transporting apparatus for transporting the substrate to the processing apparatus.
Therefore, the present method of coating protection ensures that the surface conditions of processed or to-be-processed substrates are preserved while they are waiting to be processed in the next unit processing line, thereby preventing and controlling degradation and contamination of surfaces which may be caused by exposure to a processing room atmosphere.